Association of the AAV-PRO questionnaire with established outcome measures in AAV.

OBJECTIVES: The ANCA-associated vasculitis (AAV) patient-reported outcome (AAV-PRO) questionnaire was developed to capture the impact of AAV and its treatment. We investigated the association of specific AAV-PRO domains with disease activity and extent, damage, depression, health-related quality of life, and treatment. METHODS: In a prospective longitudinal study, AAV-PRO, Beck's depression inventory (BDI), Short Form 36 (SF-36), BVAS and Vasculitis Damage Index (VDI) were completed at baseline (t1) and after 3-6 months (t2). In addition, patient data (including diagnosis, therapies, relapses, and organ manifestations) were recorded. Data were analysed by t-tests and correlation-based regression analyses. RESULTS: A total of 156 patients with AAV participated. The mean BVAS at the time of enrolment was 1.4 ± 3.74. The median AAV-PRO domain scores were higher in patients reporting 'active disease' compared with those reporting 'in remission' (P < 0.001). In the correlation analyses, all AAV-PRO domain scores correlated strongly with the BDI (all r ≥ 0.319, all P ≤ 0.001) as well as with all eight SF-36 subdomains (all |r|≥0.267, all P ≤ 0.001). The regression analyses showed that AAV-PRO domains were strongly predicted by the BDI and SF-36 domains (|ß| ≥ 0.240 for the strongest predictor of each domain). In the longitudinal comparison (t1/t2), there were no significant changes in the overall results. CONCLUSION: Our data show convergent validity for all AAV-PRO subdomains, using the established questionnaires BDI and SF-36. The AAV-PRO domains scores were not correlated with clinician-derived instruments (including the BVAS and the VDI). Thus, we regard the AAV-PRO questionnaire as a valuable measure of outcomes that might complement traditional end-points in clinical trials.

Demand-oriented design of telemedical services in gynecologic oncology.

BACKGROUND: The medical field is in the midst of a massive expansion in telemedical services. However, it is not possible to say to what extent telemedical offerings can be designed to meet needs in the German healthcare system. This study provides insights into demand-oriented care using telemedical services for gynecological patients. METHODS: A total of 262 patients who received systemic therapy for gynecological oncology were surveyed anonymously using a questionnaire regarding their acceptance of telemedicine from February 2021 to April 2021. RESULTS: Insufficient computer skills were associated with less acceptance of telemedicine treatment by gynecological oncology patients and presented a barrier. However, the patient's level of education was not related to the level of acceptance. Long travel distances from medical facilities and some types of patient occupations significantly increased the acceptance of telemedicine services. A high level of education, on the other hand, was not associated with the approval of telemedical approaches. Long journeys and work commitments increased the acceptance of telemedical visits. CONCLUSIONS: The results of this study show that the factors investigated have an influence on the acceptance of telemedical offerings by patients. Barriers such as insufficient computer skills must be taken into account when implementing telemedicine services. Telemedicine can provide physical and economic relief for patients if telemedical planning is tailored to their needs.

Long-term prognostic factors for PRRT in neuroendocrine tumors.

Aim/introduction: Peptide receptor radionuclide therapy (PRRT) is an effective and well-tolerated treatment option for patients with neuroendocrine tumors (NETs) that prolongs progression-free survival (PFS). However, the limited overall survival (OS) rates in the prospective phase III study (NETTER1) highlighted the need to identify patient-specific long-term prognostic markers to avoid unnecessary side effects and enable better treatment stratification. Therefore, we retrospectively analyzed prognostic risk factors in NET patients treated with PRRT. Methods: A total of 62 NET patients (G1: 33.9%, G2 62.9%, and G3 3.2%) with at least 2 cycles of PRRT with [177Lu]Lu-HA-DOTATATE (mean 4 cycles) were analyzed. Of which, 53 patients had primary tumors in the gastroenteropancreatic (GEP) system, 6 had bronchopulmonary NET, and 3 had NET of unknown origin. [68Ga]Ga-HA-DOTATATE PET/CT scans were performed before PRRT start and after the second treatment cycle. Different clinical laboratory parameters, as well as PET parameters, such as SUVmean, SUVmax, and PET-based molecular tumor volume (MTV), were collected, and their impact on the OS was investigated. Patient data with a mean follow-up of 62 months (range 20-105) were analyzed. Results: According to interim PET/CT, 16 patients (25.8%) presented with partial response (PR), 38 (61.2%) with stable disease (SD), and 7 (11.3%) with progressive disease (PD). The 5-year OS was 61.8% for all patients, while bronchopulmonary NETs showed poorer OS than GEP-NETs. Multivariable Cox regression analysis showed that chromogranin A level and MTV together were highly significant predictors of therapeutic outcome (HR 2.67; 95% CI 1.41-4.91; p = 0.002). Treatment response was also influenced by the LDH level (HR 0.98; 95% CI 0.9-1.0; p = 0.007) and patient age (HR 1.15; 95% CI 1.08-1.23; p < 0.001). ROC analysis revealed baseline MTV > 112.5 ml [Sens. 91%; Spec. 50%; AUC 0.67 (95% CI 0.51-0.84, p = 0.043)] and chromogranin A >1,250.75 µg/l [Sens. 87%; Spec. 56%; AUC 0.73 (95% CI 0.57-0.88, p = 0.009)] as the best cutoff values for identifying patients with worse 5-year survival. Conclusion: Our retrospective analysis defined MTV and chromogranin A in combination as significant prognostic factors for long-term OS. Furthermore, an interim PET/CT after two cycles has the potential in identifying non-responders who may benefit from a change in therapy at an early stage.

Accuracy of full-guided vs. pilot-guided implant insertion - A prospective laboratory study in fifth-year dental students.

BACKGROUND: Education of undergraduates in implant dentistry has been extended. In order to assess the correct implant position, the accuracy of implant insertion using templates for pilot-drill guided and full-guided implant insertion was examined in a laboratory set-up in a cohort of undergraduates. METHODS: After three-dimensional planning of the implant position in partially edentulous mandibular models, individual templates for the pilot-drill guided or full-guided implant insertion in the region of the first premolar were produced. A total of 108 dental implants were inserted. The results of the radiographic evaluation of the three-dimensional accuracy were statistically analyzed. Furthermore, the participants completed a questionnaire. RESULTS: The deviation of the three-dimensional angle of the implants inserted fully guided was 2.74 ± 1.49 degrees compared to 4.59 ± 2.70 degrees for pilot-drill guided. The difference was statistically significant (p < 0.01). The returned questionnaires revealed a high interest in oral implantology and a positive evaluation of the hands-on course. CONCLUSIONS: In this study, the undergraduates benefited from applying full-guided implant insertion considering the accuracy in this laboratory examination. However, the clinical effects are not clear as the differences are within a small range. Based on the returned questionnaires, the implementation of practical courses in the undergraduate curriculum should be encouraged.

The Impact of Injury of the Tibial Nutrient Artery Canal on Type of Nonunion of Tibial Shaft Fractures: A Retrospective Computed Tomography Study.

RATIONALE AND OBJECTIVES: Blood supply is vital for sound callus formation. The tibial nutrient artery (TNA) is the main diaphyseal artery nurturing the tibial shaft. The objective is to investigate the impact of TNA canal (TNAC) injury on the development of atrophic, oligotrophic, and hypertrophic nonunion in patients with tibial shaft fractures. MATERIALS AND METHODS: Between January 2010 and December 2020, patients with a nonunion of a tibial shaft fracture were retrospectively included. Two readers independently evaluated the integrity of the TNAC and classified nonunion type. A multinomial regression model was utilized to evaluate if a TNAC injury has an impact on the type of nonunion. RESULTS: From an initial set of 385 patients with the diagnosis of a nonunion of the lower leg, a total of 60 patients could be finally included in the study. Most patients were males (78%), diabetic (95%), smokers (73%), and had an American Society of Anesthesiologists (ASA) score of 2 (72%). TNAC injury was noted in 24 patients (40%): an iatrogenic TNAC injury was observed in 13 (22%) patients, a traumatic TNAC injury in 11 (18%) patients. Most patients had a hypertrophic nonunion (29 patients (48%)), followed by an oligotrophic nonunion (24 patients (40%)) and lastly an atrophic nonunion (seven patients (11%)). The multinomial regression model showed that there was no impact of TNAC injury on the development of a specific type of non-union (p = 0.798 for oligotrophic vs. atrophic nonunion; p = 0.943 for hypertrophic vs. atrophic nonunion). Furthermore, patients were about four times more likely to develop an oligotrophic/hypertrophic nonunion rather than atrophic one (odds ratio 3.75 and 4.25, respectively), regardless of the presence of a TNAC injury. CONCLUSION: In the evaluated patient cohort with tibial shaft fractures, we could not find a statistically significant association between TNAC injury and type of nonunion. However, patients were almost four times more likely to develop oligotrophic or hypertrophic nonunion rather than an atrophic one although common risk factors for impaired (micro)vascular blood supply were highly prevalent in the study group. Multicenter studies with a larger number of atrophic nonunions are warranted to further evaluate this result.

Deep Learning Reconstruction for Accelerated Spine MRI: Prospective Analysis of Interchangeability.

Background Deep learning (DL)-based MRI reconstructions can reduce examination times for turbo spin-echo (TSE) acquisitions. Studies that prospectively employ DL-based reconstructions of rapidly acquired, undersampled spine MRI are needed. Purpose To investigate the diagnostic interchangeability of an unrolled DL-reconstructed TSE (hereafter, TSEDL) T1- and T2-weighted acquisition method with standard TSE and to test their impact on acquisition time, image quality, and diagnostic confidence. Materials and Methods This prospective single-center study included participants with various spinal abnormalities who gave written consent from November 2020 to July 2021. Each participant underwent two MRI examinations: standard fully sampled T1- and T2-weighted TSE acquisitions (reference standard) and prospectively undersampled TSEDL acquisitions with threefold and fourfold acceleration. Image evaluation was performed by five readers. Interchangeability analysis and an image quality-based analysis were used to compare the TSE and TSEDL images. Acquisition time and diagnostic confidence were also compared. Interchangeability was tested using the individual equivalence index regarding various degenerative and nondegenerative entities, which were analyzed on each vertebra and defined as discordant clinical judgments of less than 5%. Interreader and intrareader agreement and concordance (κ and Kendall τ and W statistics) were computed and Wilcoxon and McNemar tests were used. Results Overall, 50 participants were evaluated (mean age, 46 years ± 18 [SD]; 26 men). The TSEDL method enabled up to a 70% reduction in total acquisition time (100 seconds for TSEDL vs 328 seconds for TSE, P < .001). All individual equivalence indexes were less than 4%. TSEDL acquisition was rated as having superior image noise by all readers (P < .001). No evidence of a difference was found between standard TSE and TSEDL regarding frequency of major findings, overall image quality, or diagnostic confidence. Conclusion The deep learning (DL)-reconstructed turbo spin-echo (TSE) method was found to be interchangeable with standard TSE for detecting various abnormalities of the spine at MRI. DL-reconstructed TSE acquisition provided excellent image quality, with a 70% reduction in examination time. German Clinical Trials Register no. DRKS00023278 © RSNA, 2022 Online supplemental material is available for this article. See also the editorial by Hallinan in this issue.

Multiparametric Dual-Time-Point [18F]FDG PET/MRI for Lymph Node Staging in Patients with Untreated FIGO I/II Cervical Carcinoma.

[18F]FDG PET/MRI was shown to have limited sensitivity for N-staging in FIGO I/II cervical carcinoma. Therefore, this prospective study aimed to investigate the additional value of multiparametric dual-time-point PET/MRI and to assess potential influencing factors for lymph node metastasis (LNM) detection. A total of 63 patients underwent whole-body dual-time-point [18F]FDG PET/MRI 60 + 90 min p.i., and 251 LN were evaluated visually, quantified multiparametrically, and correlated with histology. Grading of the primary tumor (G2/G3) had a significant impact on visual detection (sens: 8.3%/31%). The best single parameter for LNM detection was SUVavg, however, with a significant loss of discriminatory power in G2 vs. G3 tumors (AUC: 0.673/0.901). The independent predictors SUVavg, ∆SUVpeak, LN sphericity, ADC, and histologic grade were included in the logistic-regression-based malignancy score (MS) for multiparametric analysis. Application of MS enhanced AUCs, especially in G2 tumors (AUC: G2:0.769; G3:0.877) and improved the accuracy for single LNM from 34.5% to 55.5% compared with the best univariate parameter SUVavg. Compared with visual analysis, the use of the malignancy score increased the overall sensitivity from 31.0% to 79.3% (Youden optimum) with a moderate decrease in specificity from 98.3% to 75.6%. These findings indicate that multiparametric evaluation of dual-time-point PET/MRI has the potential to improve accuracy compared with visual interpretation and enables sufficient N-staging also in G2 cervical carcinoma.

Supporting families to achieve a healthy weight development for their child with overweight/obesity using the STARKIDS intervention: study protocol for a cluster-randomized controlled trial.

BACKGROUND: Childhood and adolescent overweight and obesity are among the most serious health challenges today. Structured weight reduction programs can be helpful to reduce severe health consequences but evidence is partly scarce. The STARKIDS program aims to improve on some of these limitations and is designed to be a structured, stepwise, digitally supported intervention program for the whole family. It is divided into two intervention steps spanning over 1.5 years and aims at promoting a healthy weight development of children/adolescents with overweight/obesity and an increase in quality of life. METHODS: The STARKIDS intervention is evaluated in a cluster-randomized study design by comparing it with a control group receiving a one-time structured counselling in the pediatric practice. The study aims to include 1000 families with children/adolescents with overweight/obesity from 100 pediatric practices. The main outcomes are reduction in body mass index percentiles and improvements in children's/adolescent's quality of life, secondary outcomes refer to the contents of the intervention such as diet, physical activity, stress, and media habits. All outcomes are measured on three measurement time points: (T0) at baseline/inclusion in the study, (T1) baseline + 12 months which is the end of step 1 of the STARKIDS intervention, and (T2) baseline + 18 months which is the end of step 2 of the STARKIDS intervention. DISCUSSION: The stepwise, e-health-supported STARKIDS program is a low-threshold intervention program for families with children/adolescents with overweight/obesity. With the proof of concept, STARKIDS provides the potential to be implemented as a standard care tool for the prevention and intervention of childhood/adolescence obesity in the German health system. TRIAL REGISTRATION: German Clinical Trials Register (DRKS) DRKS00022813  (acknowledged primary register of the World Health Organization). Registered on 27 November 2020 (Universal Trial Number U1111-1254-9536).

Fully Automated Artery-Specific Calcium Scoring Based on Machine Learning in Low-Dose Computed Tomography Screening.

PURPOSE: Evaluation of machine learning-based fully automated artery-specific coronary artery calcium (CAC) scoring software, using semi-automated software as a reference. METHODS: A total of 505 patients underwent non-contrast-enhanced calcium scoring computed tomography (CSCT). Automated, machine learning-based software quantified the Agatston score (AS), volume score (VS), and mass score (MS) of each coronary artery [right coronary artery (RCA), left main (LM), circumflex (CX) and left anterior descending (LAD)]. Identified CAC of readers who annotated the data with semi-automated software served as a reference standard. Statistics included comparisons of evaluation time, agreement of identified CAC, and comparisons of the AS, VS, and MS of the reference standard and the fully automated algorithm. RESULTS: The machine learning-based software correlated strongly with the reference standard for the AS, VS, and MS (Spearman's rho > 0.969) (p < 0.001), with excellent agreement (ICC > 0.919) (p < 0.001). The mean assessment time of the reference standard was 59 seconds (IQR 39-140) and that of the automated algorithm was 5.9 seconds (IQR 3.9-16) (p < 0.001). The Bland-Altman plots mean difference and 1.96 upper and lower limits of agreement for all arteries combined were: AS 0.996 (1.33 to 0.74), VS 0.995 (1.40 to 0.71), and MS 0.995 (1.35 to 0.74). The mean bias was minimal: 0.964-1.0429. Risk class assignment showed high accuracy for the AS in total (weighed κ = 0.99) and for each individual artery (κ = 0.96-0.99) with corresponding correct risk group assignment in 497 of 505 patients (98.4 %). CONCLUSION: The fully automated artery-specific coronary calcium scoring algorithm is a time-saving procedure and shows excellent correlation and agreement compared with the clinically established semi-automated approach. KEY POINTS: · Very high correlation and agreement between fully automatic and semi-automatic calcium scoring software.. · Less time-consuming than conventional semi-automatic methods.. · Excellent tool for artery-specific calcium scoring in a clinical setting.. CITATION FORMAT: · Winkelmann MT, Jacoby J, Schwemmer C et al. Fully Automated Artery-Specific Calcium Scoring Based on Machine Learning in Low-Dose Computed Tomography Screening. Fortschr Röntgenstr 2022; 194: 763 - 770.

Substantial changes in fracture rates in German hospitals in 2018 compared with 2002: an epidemiological study.

INTRODUCTION: The aim of this study was to present recent epidemiological data on extremity and axial skeletal fractures in German hospitals and to compare them with older data to detect time trends. MATERIALS AND METHODS: Inpatient data from the German National Hospital Discharge Registry were used. The absolute number and age-standardized incidence of fractures in 2002 and 2018 were analysed by fracture location according to the International Classification of Disease. Data were analysed according to age group. Male: female ratios (MFRs) and incidence rate ratios (IRRs) were calculated to compare the 2018 and 2002 data. RESULTS: The absolute number of fractures of the nine analysed locations was 15.2% higher in 2018 than in 2002. By fracture location, the changes were as follows (absolute change + IRR): "neck" (S12): + 172%, IRR = 2.6; "rib(s), sternum, thoracic spine" (S22): + 57%, IRR = 1.3; "lumbar spine and pelvis" (S32): + 66%, IRR = 1.3; "shoulder and upper arm" (S42): + 36%, IRR = 1.2; "forearm" (S52): + 13%, IRR = 1.0; "wrist and hand level" (S62): - 32%, IRR = 0.7; "femur" (S72): + 24%, IRR = 0.9; "lower leg, including ankle" (S82): - 24%, IRR = 0.7; "foot, except ankle" (S92): - 4%, IRR = 0.9. The overall MFR changed from 0.7 in 2002 to 0.6 in 2018. The age group of 45-54 years represented a turning point, males were more often affected than females in the younger age groups, and the opposite trend was observed in the older age groups. CONCLUSIONS: The increase in the absolute fracture rates was due to increased rates of femur, shoulder, upper arm, forearm, and axial skeletal fractures, with elderly women being the main contributors. Femur fractures were found to be the most common fractures treated in German hospitals.

Fluid-based augmentation of magnetic resonance visualization of interventional devices.

PURPOSE: To evaluate the transient artifact augmentation of microtubes in magnetic resonance imaging by fluid injection. METHODS: Twenty-one fluorinated ethylene propylene catheters (inner diameter 760 µm) were filled with three different contrast media at various concentrations (Ferucarbotran, Resovist®, Bayer Schering Pharma; Manganese dichloride, MnCl2, Sigma-Aldrich; Gadobutrol, Gadovist®, Bayer Schering Pharma). Artifact appearance was determined in an ex vivo phantom at 1.5 T using three different sequences: T1-weighted three-dimensional volume interpolated breath-hold examination, T2-weighted turbo spin echo, and T1-weighted fast low angle shot. Catheter angulation to the main magnetic field (B0) was varied. Influence of parameters on artifact diameters was assessed with a multiple linear regression similar to an analysis of variance. RESULTS: Artifact diameter was significantly influenced by the contrast agent (p < 0.001), concentration of the contrast agent (p < 0.001), angulation of the phantom to B0 with the largest artifact at 90° (p < 0.001), and encoding direction with a larger diameter in phase encoding direction (PED, p < 0.001). Mean artifact diameters at 90° angulation to B0 in PED were 18.5 ± 5.4 mm in 0.5 mmol/ml Ferucarbotran, 8.7 ± 2.5 mm in 1 mmol/ml Gadobutrol, and 11.6 ± 4.6 mm in 5 mmol/ml MnCl2 . CONCLUSIONS: Fluid-based contrast agents might be applied to interventional devices and thus temporarily augment the artifact ensuring both visibility and safe navigation.

Extubation and Noninvasive Ventilation of Patients Supported by Extracorporeal Life Support for Cardiogenic Shock: A Single-Center Retrospective Observational Cohort Study.

BACKGROUND: Temporary extracorporeal life support (ECLS) by venoarterial extracorporeal membrane oxygenation is an emerging therapy for patients with severe, ongoing cardiogenic shock. After stabilization of the hemodynamic status and end-organ function, sedation weaning, extubation, and noninvasive ventilation (NIV) can be attempted. The goal of this study was to analyze the feasibility of extubation and NIV during versus after ECLS for cardiogenic shock. METHODS: Single-center retrospective observational study of 132 patients undergoing ECLS due to severe cardiogenic shock between January 2015 and December 2016 at a tertiary care university hospital. RESULTS: Patients received ECLS due to acute myocardial infarction (20.6%), ongoing cardiogenic shock (15.2%), postoperative low-cardiac-output syndrome (24.2%), and extracorporeal cardiopulmonary resuscitation (40.2%). Overall, intensive care unit survival was 44.7%. Sixty-nine (52.3%) patients could never be extubated. Forty-three (32.6%) were extubated while on ECLS support (group 1) and 20 (15.1%) were extubated after weaning from ECLS (group 2). Patients extubated during ECLS had a significantly shorter total time on ventilator (P = .003, mean difference: -284 hours [95% confidence limits: -83 to -484]) and more invasive ventilation free days (P = .0018; mean difference 8 days [95%CL: 2-14]). Mortality and NIV failure rates were similar between groups. CONCLUSIONS: Extubation and NIV are feasible in patients who stabilize during ECLS therapy. Further studies need to address whether extubation has the potential to improve patients outcome or if the feasibility to extubate is a surrogate for disease severeness.

Assessment of tobacco heating system 2.4 on osteogenic differentiation of mesenchymal stem cells and primary human osteoblasts compared to conventional cigarettes.

BACKGROUND: Cigarette smoking (CS) is the most common method of consuming tobacco. Deleterious effects on bone integrity, increased incidence of fractures, and delayed fracture healing are all associated with CS. Over 150 of the 6500 molecular species contained in cigarette smoke and identified as toxic compounds are inhaled by CS and, via the bloodstream, reach the skeletal system. New technologies designed to develop a reduced-risk alternative for smokers are based on electronic nicotine delivery systems, such as e-cigarettes and tobacco heating systems (THS). THS are designed to heat tobacco instead of burning it, thereby reducing the levels of harmful toxic compounds released. AIM: To examine the effects of THS on osteoprogenitor cell viability and function compared to conventional CS. METHODS: Human immortalized mesenchymal stem cells (n = 3) and primary human pre-osteoblasts isolated from cancellous bone samples from BG Unfall Klinik Tübingen (n = 5) were osteogenically differentiated in vitro with aqueous extracts generated from either the THS 2.4 "IQOS" or conventional "Marlboro" cigarettes for up to 21 d. Cell viability was analyzed using resazurin conversion assay (mitochondrial activity) and calcein-AM staining (esterase activity). Osteogenic differentiation and bone cell function were evaluated using alkaline phosphatase (AP) activity, while matrix formation was analyzed through alizarin red staining. Primary cilia structure was examined by acetylated α-tubulin immunofluorescent staining. Free radical production was evaluated with 2',7'-dichlorofluorescein-diacetate assay. RESULTS: Our data clearly show that THS is significantly less toxic to bone cells than CS when analyzed by mitochondrial and esterase activity (P < 0.001). No significant differences in cytotoxicity between the diverse flavors of THS were observed. Harmful effects from THS on bone cell function were observed only at very high, non-physiological concentrations. In contrast, extracts from conventional cigarettes significantly reduced the AP activity (by two-fold) and matrix mineralization (four-fold) at low concentrations. Additionally, morphologic analysis of primary cilia revealed no significant changes in the length of the organelle involved in osteogenesis of osteoprogenitor cells, nor in the number of ciliated cells following THS treatment. Assessment of free radical production demonstrated that THS induced significantly less oxidative stress than conventional CS in osteoprogenitor cells. CONCLUSION: THS was significantly less harmful to osteoprogenitor cells during osteogenesis than conventional CS. Additional studies are required to confirm whether THS is a better alternative for smokers to improve delays in bone healing following fracture.

Injury of the Tibial Nutrient Artery Canal during External Fixation for Lower Extremity Fractures: A Computed Tomography Study.

The tibial nutrient artery (TNA) is the major diaphyseal artery of the tibia supplying two thirds of the inner osseous cortex. Hence, iatrogenic injury of the TNA endangers the integrity of the tibial blood supply and may compromise fracture healing. The incidence of its injury in the setting of external fixation for lower limb fractures has not been previously investigated. The aim of this study was to evaluate the incidence of TNA injury in the context of external fixation and to characterize the topography of the fixator pins in relation to the TNA canal (TNAC). Patients who underwent external fixation for distal femoral fractures and for tibial (proximal, shaft, and distal) fractures and had a postoperative computed tomography study were retrospectively included. The following parameters were retrieved: 1) Pin characteristics (orientation and cortical position of the pins), 2) The anatomic relationship between the TNAC and external fixation pin (topography above/below and at the level of the TNAC, and the distance between the pin and medial tibial plateau and/or the medial malleolus), and 3) The incidence of TNAC injury (complete/partial disruption of TNA lumen). A total of 105 patients with 214 tibial pins were analyzed. In 27 patients (26%), the TNAC was completely injured by the pins of the external fixator. In 13 patients (12%), the TNAC was partially injured. Of the 214 analyzed pins, 85 pins (40%) were located at the level of the TNAC (the TNAC and the pin are seen on the same axial slice). Most pins that were applied at the level of the TNAC belonged to a knee-bridging external fixator. Of those, ninety-three percent of the pins were anteromedially applied according to published surgical guidelines. Six percent of the pins were applied through the tibial crest and 1% anterolaterally. Of those 85 pins, 42 pins (49%) injured the TNAC at least partially. Based on the analyzed pins and the incidence of partial and complete injury of the TNAC, we observed that the tibial segment at which the tibial nutrient artery is endangered was located approximately (95% CI: 13-15 cm) from the medial tibia plateau and (95% CI: 22-25 cm) from the medial malleolus. Thus, TNAC injury by external fixation pins in the context of lower limb fractures can be considered common. Almost half of the pins applied at the middle third of the tibia injured the TNA, despite adherence to published surgical guidelines for external fixation. When possible, pin application at the middle third of tibia should be avoided to circumvent iatrogenic injury of the TNA and to safeguard tibial blood supply.